Synthetic nitrogenous textile coated with colloidal hydrous alumina



Nov. 23, 1965 M, LE CLERC 3,219,479

G. SYNTHETIC NITROGENOUS TEXTILE COATED WITH COLLOIDAL HYDROUS ALUMINA Filed June 22, 1962 INVENTOR GEORGE MORROW LE CLERCQ BY Maw ATTORNEY United States Patent SYNTHETIC NITROGENOUS TEXTILE COATED WiTI-I COLLOIDAL HYDROUS ALUMINA George Morrow Le Clercq, Wilmington, Del., assignor to E. L du Pont de Nemours and Company, Wilmington,

Del., a corporation of Delaware Filed June 22, 1962, Ser. No. 296,125 8 Claims. (Q1. 117138.S)

This application is a continuation-in-part of United States application Serial No. 791,536, filed February 6, 1959, now abandoned.

This invention relates to an improved textile material. More specifically, it relates to an improved textile which may have a pile or tufted surface, such as a carpet or rug, made from filaments of synthetic linear nitrogenous condensation polymer, such as a polyamide.

The use of p-olyamide fiber in the manufacture of rugs, especially for use in the pile fiber thereof, is well known. In this use, the nylon contributes outstanding wear resistance. However, such rugs are known to generate static electricity at times, and in addition can be visibly damaged by melting when lighted cigarettes, matches and the like are dropped upon them. In addition, pilling and fuzzing of nylon rugs is often experienced under some conditions of wear. The pilling and fuzzing is thought to be due to the toughness of the filaments which makes them so useful for Wear resistance. In accordance with this theory, surface filaments which are dislodged from the woven matrix appear first as fuzz, which then matts together to form the fibrous balls known as pills. Although this defect has long been observed on woolen fabrics, such as carpets, due to the low abrasion resistance of wool these pills are broken oil almost as fast as they form so that they do not accumulate to an unsightly degree. Such is not the case with polyamide carpets.

An improved product has been formed by grafting polymer chains derived from unsaturated organic acid to the polyamide of the nylon fiber and thereafter converting the acid to a metallic salt, preferably sodium, calcium or magnesium salt. Methods of preparing acid grafted synthetic linear nitrogenous condensation polymer, of which nylon is an example, are described by D. Tanner in United States application Serial No. 719,659, now United States Patent No. 3,099,631, dated July 30, 1963. In accord with these processes, a soil repellent, antistatic meltresistant fiber is prepared by grafting unsaturated organic acid to the polymer substrate so that the modified polymer bears at least 300 equivalents of acid groups per million grams of polymer, including normal polymer acid ends and those added by grafting. When fiber modified in this manner is used in the pile of a carpet, the carpet, although highly antistatic, dyeable, and resistantto soiling and to hole melting, is nevertheless subject to pilling and fuzzing.

Objects It is thus an object of the invention to provide a composition of nitrogenous condensation polymer fiber having a surface coating of colloidal hydrous alumina.

Another object is to provide a staple fabric of alumina coated, acid-grafted nitrogenous condensation polymer filaments which has a greatly reduced tendency to pill.

A further object is to provide a carpet or rug having pile filaments of the said acid-grafted polymer bearing a coating of hydrous alumina, the said carpet being characterized by a reduced tendency to fuzz and pill, in addition to being antistatic, dyeable, soil repellent, resistant to hole melting and abrasion resistant.

These and other objects will become apparent in the course of the following specification and claims.

Statement of invention In accordance with the present invention fuzzing and pilling of a fabric, such as a carpet, formed from fibers of anacid-grafted synthetic linear nitrogenous condensation polymer, such as nylon, can be reduced by wetting the fibers with a sol of hydrous alumina having at least one dimension in the colloidal range, preferably at a temperature of at least about C., and thereafter drying the said fibers. The product formed is a novel and useful article of manufacture, comprising (a) a coating of from about 0.5 to about 5% of colloidal particles of hydrous alumina, deposited upon (b) fibers or filaments of an acid grafted synthetic linear nitrogenous condensation polymer, at lea-st the surface layer of said fibers or filaments being modified to contain, for each million grams of polymer, at least 300 equivalents of radicals selected from the group consisting of acid and metallic salt of acid, chemically bonded by carbon-carbon bonds to the said polymer. By acid radical is intended all those radicals which produce acidity other than phenolic acidity.

Alumina treatment of filaments of nitrogenous condensation polymer which have not been previously acidmodified, provides no significant improvement in resistance to pilling and fuzzing; the presence of at least 300 equivalents of acid radical or salt thereof is required to obtain the benefits .of the instant invention. While larger amounts (e.-g., 3000 equivalents) of acid or acid salt are often beneficial, for example, to reduce the level of static or provide resistance to hole melting, these larger amounts are not effective to improve pilling and 'fuzzing. It is obvious that the concentration of grafted acid should not be large enough to make the fiber water soluble or sensitive to alkaline scour.

Illustrations The invention will be more readily understood by reference to the illustrations. FIGURE I shows a fiber of acid-grafted water insoluble synthetic linear nitrogenous condensation polymer 1 bearing as a coating spherical particles of hydrous alumina a.

FIGURE II is a cross-sectional elevation of the structure of FIGURE I.

FIGURE III shows the fiber of FIGURE I containing a coating of fibrous hydrous alumina particles.

Definitions The term synthetic linear nitrogenous condensation polymer is intended to describe a class of substantially linear condensation polymers in which nitrogen atoms occur as part of the polymer molecule backbone. The best known representatives of this class are the polyamides, which are characterized by recurring links in the polymer chain, where R may be hydrogen or organic radical. High molecular weight polyamides,

now well known as nylon, are especially preferred in forming the modified filament substrate for the process of this invention. Other well known polymers comprehended in the defined class are the polyurethanes, characterized by recurring if NCO links, and polyureas, characterized by i i N J N groups. Also included are those polymers with recurring main chain links such as ORR and the like. The R substituents on the nitrogen are preferably hydrogen, but may be monovalent radical, preferably hydrocarbon radical. In addition to the above, polysulfonamides may be employed.

The presence of nitrogen as units in the polymer chain is the feature which characterizes the polymers useful in forming the acid-modified filaments to which the alumina is applied. It is believed that the nitrogen atom in the carbonamide or sulfonamide type radical activates nearby and especially the adjacent carbon-hydrogen groups so that hydrogen is readily abstracted by free-radical initiators, forming a free radical which thus becomes available for attachment of acid groups, as explained hereinafter. It has been established that this class of polymers is more readily graftable than a polymer of similar structure without said atoms. Thus, cop'olymers are included among the polymers suitable for forming the product of this invention, provided they contain at least about 1.0% by weight of atom as an integral part of the polymer chain.

The term synthetic linear organic condensation polymer is Well understood; it refers to those polymers which are formed in condensation reactions wherein simple molecules are eliminated, such as H 0, H01, NaCl, NH and the like, also those polymers which on chemical degradation (e.g., by hydrolysis) yield monomeric end products differing in composition from the structural units (Flory, Principles of Polymer Chemistry, Cornell Univ. Press, Ithaca, N.Y., 1953). These polymers usually have a repeating unit with structural formula different from the formula of the monomer, in contrast to addition polymers formed by addition via an unsaturated carbon-carbon bond. Again unlike addition polymers, a monomer can usually be obtained from a condensation polymer by hydrolysis. Although some condensation polymers may be prepared from certain monomeric derivatives whereby the elimination of simple molecules is not required, these are 'not exceptions to the defined class; in this case, the simple molecule has already in effect been eliminated from the monomer. Examples of such monomeric compounds are acid anhydrides, lactones and lactams. For example, a polyamide may be prepared from an amino carboxylic acid with the evolution of water molecules. On the other hand, the identical polymer may be prepared from the epsilon lactam derivative of that amino carboxylic acid, but in this case no water need be eliminated. The synthetic organic condensation polymers used to form the product of this invention are those which are primarily carbonaceous in character, i.e., have polymer chains which consist primarily of carbon-carbon bonds, interrupted periodically by other atoms such as nitrogen in the polymer chain.

Many of these polymeric substrates may bear acid end groups which remain after the polymerization has been completed. However, when such polymers have a sufficiently high molecular weight to form filaments, fewer than equivalents of acid (per 10 gm. polymer) remain. Thus, there are insuflicient acid groups to attain the minimum of 300 required to provide the antistatic meltand soil-resistant textile. Additional acid groups are therefore attached to the substrate nitrogenous condensation polymer by treating it with unsaturated organic acid such as for example acrylic acid, methacrylic acid, styrene sulfonic acid, ethylene sulfonic acid, maleic acid, crotonic acid, to name but a few, for such time and temperature that the acid penetrates into the polymer substrate. Free radicals are generated upon the molecules of the polymer substrate, for example, by high energy irradiation With electrons or X-rays, by heating in the presence of a free radical initiator such as ammonium persulfate, or exposure to ultraviolet irradiation, preferably in the presence of a photo-initiator. The free radicals on the polymer backbone initiate vinyl polymerization and the unsaturated acid is grafted to the substrate polymer. As stated hereinbefore, a minimum concentration of total acid groups of 300 or more per million grams of polymer is required.

Following the grafting reaction, excess monomer and ungrafted homopolymer are removed by extraction with water; the acid-modified filaments prepared as described hereinabove may then be converted completely or in part to the preferred metal salt by boiling in a dilute solution of the metal ion, for example as the hydroxide, carbonate or acetate. Filaments formed from the graft polymer as described above are treated with hydrous alumina sol, to form the product of the present invention, i.e., a highly useful staple yarn product which is free from fuzzing and pilling.

Various forms of alumina in sols, gels, etc., are known and the literature pertaining thereto is extensive. The essential characteristic of the aluminas suitable in preparing the pill-resistant acid-modified filaments of the present invention is that they have at least one dimension in the colloid range when dispersed in water or other suitable liquid.

Test materials and methods Carpets used in the following examples are prepared by conventional tufting or Weaving methods, using a pile yarn of poly(hexamethylene adipamide), a nylon representing the defined class of nitrogenous condensation polymer.

The fibrous boehmite alumina used in treating the fabrics of the instant invention is described and claimed by Bugosh in United States Serial No. 730,025, now abandoned, and is prepared as follows:

An alumina gel is precipitated by simultaneously metering an alum solution containing 1 part Al (SO 18 H O and 2 parts distilled water and a sodium carbonate solution containing 1 part Na CO and 4 parts distilled water into the agitated reaction mass in an open tank. The reactant ratio, CO /Al, is maintained at l.70i0.02 (molar basis) at all times during the precipitation. After precipitation the gel slurry is transferred to a filter Nutsche and filtered using vacuum. The filter cake is washed on the Nutsche using nine successive washes of distilled water at 70 C. Each wash volume is approximately equivalent to the volume of the filter cake. The

washed cake is homogenized by mixing 3151 parts cake with 850 parts water in a laboratory Waring Blendor. This homogenized slurry analyzed as:

The alumina content here will be expressed as percent A1 although this does not necessarily show the degree of hydration in a specific aluminum compound present. Two thousand two hundred parts of this slurry are aged' for 24 hours at 25 C. and then mixed with 1218 parts distilled water and 82.4 parts glacial acetic acid. This mixture is placed in a flask equipped with a paddle agitator and heated to boiling (100 C.) and held at reflux for 5 minutes to drive off carbon dioxide. This re action mix is then transferred to a stainless steel autoclave equipped with an agitator and heated to 160 C. in a period of 24 minutes. Temperature is maintained at 160 C. for one hour and then the charge is cooled to 70 C. in minutes and discharged from the autoclave. After drying the sol the fibrous alumina monohydrate powder has the following composition:

The particles of product are small fibrils with a length of about 300 millimicrons and a diameter of 3 to millimicrons.

A second alumina used in the examples is a commercial product sold by G. L. Cabot Co., Boston, Massachusetts, under the name of Alon-C. This product is an alumina predominantly in the gamma Al O configuration. The ultimate particles are spherical and the diameter range is 1040 millimicrons. On a moisture free basis, the analysis is: A1 0 95% minimum; total non A1 0 oxides, 0.2% maximum; free moisture (105 C.), 2% maximum; ignition loss (1000 C.), 3% maximum. This compound forms a sol in water.

A third hydrous alumina used in the examples, having some particles outside the range useful in preparing the product of this invention, is a commercial product sold by the Aluminum Company of America, and coded C- 730. This compound is a hydrated alumina, which is mainly Al(OH) in the gibbsite crystalline form. This product contains a large proportion of colloidal material (average particle diameter 50 millimicrons). A typical analysis is 64.4% A1 0 34.9% combined water, 0.2% water and 0.5% Na O. This compound forms a sus pension when dispersed in water.

The degree of acid modification (equivalents of acid groups per 10 gm. polymer) of the polymer substrate may be determined by titration. A suitable method is to boil the fiber sample in aqueous 0.1 N sodium hydroxide, followed by bacl; titrating the excess base with 0.1 N HCl using bromo-cresol green indicator.

The pilling and fuzzing test is carried out as follows:

The carpet samples to be tested are cut into specimens 8 inches square, and two such carpet squares are stapled together back to back with a piece of cardboard between them to act as a stiffener and prevent curling.

Six to eight of these sandwiches are loaded into the drum of a conventional domestic tumble-type clothes dryer that is equipped to blow unheated air through the drum. The dryer drum is also loaded with the following items:

(1) Thirty strips of natural rubber sheet (Durometer A [Shore Instrument and Manufacturing Co., Jamaica, New York] hardness about 40, size 18% inches x 5% inches x inch)8 pounds.

(2) Five strips of neoprene sheet (Durometer A, hard- 6 ness about 50, size 17% inches x 5% inches x 4; inch)- 3 pounds. Each neoprene strip has 20 to 30 one-inch diameter holes to increase the snagging type of abrasion. (3) Six balls of tightly rolled cotton rags (5 inches in diameter)3 pounds.

This load, which Weighs about 20 pounds, is then tumbled for the specified test period. At the end of the tumbling period, the samples are removed, unstapled, the edges trimmed and beveled, and the surface brushed lightly to remove loose lint and to erect the pills. The samples are evaluated subjectively by a panel of several persons. Numerical ratings are given to each sample, as indicated below:

Textile condition: Rating No pilling and fuzzing 1 Slight pilling and fuzzing 2 Moderate pilling and fuzzing 3 Heavy pilling and fuzzing 4 Severe pilling and fuzzing 5 This test has been found to give a good correlation with actual floor wear tests.

The invention is illustrated by the following examples. They are not intended to limit it in any way.

EXAMPLE 1 A series of ten-pound samples of crimped nylon tow, coded 1A to 1F, is prepared from drawn polyhexamethylene adipamide yarn of 15 denier per filament, each filament having a Y cross section using a spinneret with a Y patterned arrangement of orifices (United States application No. 334,457, filed February 2, 1953). The tow is padded with aqueous acrylic acid solution in concentrations ranging from 10 to 50% by weight. The padding ratio is adjusted so that a range of modification is obtained as illustrated in Table I. After padding, the samples are placed in a tray and exposed to an electron beam of a Van de Gratf accelerator of 2 m.e.v. electrons to a dose of 1 mrad. The irradiated tow is fed directly from the tray into a tap water rinse bath at 90 C. where it is subjected to a three-minute wash. After re moving samples from each portion for analysis, the samples 1A to IE inclusive now hearing grafted acrylic acid, are soaked in 1% aqueous sodium carbonate at a temperature of -95 C. An exposure time of 10 minutes is employed; this step converts the grafted acid in part to the sodium salt. Unreacted sodium carbonate is removed from the tow by rinsing with distilled water. Samples 1D, 1E and IF are next converted from the sodium to the calcium salt by soaking in a 3.7% solution of aqueous calcium acetate at room temperature for 30 minutes. Excess salt is removed as before. The six samples of tow are then dried, sampled, and cut into staple, along with an unmodified (non-irradiated) nylon control, 1G. Analyses showing carboxyl concentration, and percent conversion to sodium or calcium salt respectively (determined by analyses) are indicated in Table 1. Each sample is spun into yarn using a modified cotton system; the yarn is 0.7 wool run singles, and is doubled to give a two-ply 3 Z/4 S yarn in final twist. The yarn is then tufted onto jute backing to form panels of both loop and cut construction with a pile height of and a stitch density of 5 per inch. The pile of each carpet representing samples 1A to 11F is treated with an aquasol containing 0.45% of the fibrous boehmite alumina, after which the carpets are dried and coated with latex on the bottom side, in conventional manner. Representative samples of each item are evaluated for pilling and fuzzing in a ten hour tumble test, previously described. The results are indicated in Table I.

TABLE I Percent Wt. Percent Pill and fuzz test Samples Equiv. acid conversion AlOOH per g. to salt picked up Test Control* Sodium salt form:

*No alumina sol applied.

EXAMPLE 2 When the technique of the example is applied to poly- Fifteen pounds of 2 /2" cut polyhexamethylene adipamide staple is soaked in 25% aqueous acrylic acid at room temperature for hours. It is then centrifuged until a solution ratio of 0.30 gram of solution per gram of dry nylon is obtained. The Wet staple is irradiated using 2 m.e.v. electrons and a dose of 1 mrad. The excess acrylic acid and non-grafted homopolymer is washed out with boiling distilled water. Analysis shows the carboXyl group content to be 1549 equivalents per 10 gram. The staple is dried, opened, carded and spun on the modified cotton system and processed into loop tufted carpets as described in Example 1. After forming the carpet, the acid-modified nylon is converted to the sodium salt form (prior to lateXing) by heating for /2 hour at the boil in 0.4% sodium carbonate solution. A fabric-tobath ratio of 1-150 is employed, based on the weight of pile yarn. The treatment converts the acid groups in the nylon to the sodium salt form with an 80% complete conversion. Excess salt is removed by two five-minute rinses in distilled water.

Swatches of the thus treated carpet are soaked in the alumina dispersions identified in Table II. A bath ratio 4.0

then latexed, brushed and sheared. Eight inch square samples are then subjected to tumbling in the pilling and fuzzing test, previously described, with the results shown in Table II.

(caproamide) yarn, acid grafted to the equivalent extent with acrylic acid, similar results are obtained.

The sodium salt form of the acid modified nylon yarn used to prepare samples 2A, 2B and 2C above is made up into two other sample series of two skeins each, each series containing, in addition, an unmodified 66 nylon comparative control and each sample containing 1% by weight alumina. In one series, labelled 2D, 2E and 2H, the alumina is deposited from boehmite alumina sol, whereas in the other series labelled 2F, 26 and 21, alumina is applied by padding with Alon-C sol. Samples 2H and H are the comparative controls. All skeins are air dried at room temperature, then skeins 2D, 2F, 2H and 21 are heated for one hour at 150 C. All six skeins are then given an alkaline scour (pH=9) at the boil for one hour. The alkaline bath contained 100 parts water, 0.50 part sodium lauryl sulfate-sodium polyphosphate detergent, and 0.25 part sodium hexametaphosphate. The skeins are then rinsed, dried, converted to carpet and subjected to the pilling tests. Carpets 2D and 2F are commercially acceptable, whereas carpets 2E and 2G are no better than untreated control 2C. Carpets 2H and 21 are not commercially acceptable. This heat treating the a'crylate-grafted yarn bearing the alumina sol on its surface makes it durable to resist an alkaline scour. Heat treatment is ineffective to make alumina treated, nongrafted nylon durable to alkaline scour.

Comparable results are obtained when acrylate-grafted nylon skeins are heated in the alumina sols for two minutes at 100 C., and dried at room temperature.

When the control sample, 2C, of unmodified (not acidgrafted) nylon (otherwise equivalent in construction to test samples 2A and 2B) is treated with either of the aluminas no improvement in pilling and fuzzing is noted over the untreated control listed in the table.

Following the pilling test, the carpet samples are given two consecutive commercial washings, which involve a brush-jet cleaning with an aqueous shampoo solution predominantly containing sodium phosphate, followed by rinsing with tap water; the washings are carried out at room temperature. Following the washing, the samples are analyzed for aluminum content. These results are also indicated in Table II. The 0.5% alumina retained after the washings of Sample 2A provides continued protection from pilling and fuzzing. Carpet 2B, with less than 0.4% alumina retained after washing, is not considtection.

5 is then washed with hot distilled water.

EXAMPLE 3 Polyhexamethylene adipamide tow is soaked in 20% aqueous acrylic acid solution for 1.7 minutes at C. It is then freed of excess acrylic acid solution by passing through squeeze rolls at medium pressure and irradiated with 2 m.e.v. electrons to a dose of 1.5 mrads. The tow The dried material has a carboXyl group content of 1894 equivalents per 10 grams, which is equivalent to a weight gain of 15.2%. The tow is crimp'ed and cut to 3-inch staple, opened, carded and spun to yarn on the woolen system. The yarn is converted to the sodium salt by heating at the boil for /2 hour in 0.4% sodium carbonate solution, using a yarn to bath ratio of 1:150. After the yarn is rinsed in distilled water and dried, analysis shows that of the free carboXyl groups in the yarn have been converted to the sodium salt form.

The resulting yarn is woven to a loop pile carpet having a pile height of 3 inch and 39 ounces of pile yarn per square yard. Sections of this carpet are soaked for 30 minutes in alumina dispersions as indicated in Table IIIa a carpet-to-bath weight ratio of 1:20. The sections are passed through a wringer, rinsed in cold distilled water for minutes (at a bath ratio of 1:50), passed through the wringer, rinsed again and passed through the wringer and dried at 75 C. Eight-inch square samples are subjected to tumbling in the pilling and fuzzing test with the results shown in Table 1110.

* Grafted control.

A portion of the carpet prepared above is processed to convert the carboxyl groups to the magnesium salt form by soaking for minutes at room temperature in 5% aqueous magnesium acetate at a carpet-bath ratio of 1:20. The treated carpet is passed through a wringer, rinsed 10 minutes in cold distilled water at a bath ratio of 1:50, passed through the wringer, rinsed again the passed through the wringer and dried at C. Analysis of this carpet indicates that of the carboxyl groups are in the form of the magnesium salt. This carpet is treated with alumina dispersions and tumbled in the pilling and fuzzing test with the results shown in Table Illb. The control is Mg-acrylate grafted.

In this case, owing to a low pickup of the fibrous boehmite alumina (identified as boehmite in the tables), the magnesium salt being less effective in pickup ability for this alumina than the sodium salt discussed above, no improvement in pilling and fuzzing over the control sampie is obtained.

EXAMPLE 4 Polyhexamethylene adipamide tow of 15 denier per filament is acid grafted as in Example 3, followed by recrimping and cutting to 3-inch staple. In order to avoid shrinkage of the yarn which occurs on initial conversion to the sodium salt form, the staple is converted to the sodium salt by boiling for /2 hour in 0.4% sodium carbonate solution. Approximately conversion is obtained. The staple is then reconverted to the acid form (for more convenient processing) by boiling for 1 hour in 2% acetic acid solution, followed by drying. The dried acid-regenerated staple is carded and spun on the woolen system and is plied 4 Z, 2 /2 S twist to a final yarn count of 7 s woolen count. The plied yarn is then reconverted to the sodium salt in dye cones by boiling for /2 hour in' 0.4% sodium carbonate solution, as in Example 3.

The resulting yarn is woven to a loop pile carpet as described in Example 3, and sections of this carpet are soaked for 30 minutes at room temperature in the alumina solutions indicated in Table IVa. A sample-to-solution ratio of 1:50 is used for sample 4C, whereas a ratio 1:20 is used for the other samples. After soaking for 30 minutes, the samples are centrifuged, rinsed in distilled water for 10 minutes, again centrifuged, followed by a second rinse, another centrifuge step, and are then dried in air at 75 C. Samples of the pile yarn are taken for analysis, with the results indicated in Table IVa. The samples are then subjected to the standard pilling test for 10 hours, as described hereinabove. A control (46) is included which has not been sodium-acrylate modified or alumina treated. The results of the pillirig test are also listed in Table IVa.

TABLE IVtir-ALUMINA TREATMENT OF ACRYLATE- GRAFTED NYLON *Alumina sol is sprayed onto pile of sample to obtain 2.0% pickup.

Comparable samples of carpet are prepared from nylon yarn which has not been modified by acid grafting. These carpets are treated similarly, using the alumina sols listed in Table IVb. In some cases, low alumina pickup is observed, and in no case is there a significant improvement in pilling.

TABLE IVb.-ALUMINA TREATMENT OF UNMODIFIED NYLON Dispersion Percent Sample Alumina used composition pickup based Pilling wt. percent on wt. pile test fiber EXAMPLE 5 Applying the alumina sol to the fiber at temperatures exceeding C. not only improves durability of the alumina, to scouring, but also to abrasion, thus increasing its effectiveness versus pilling and fuzzing, as shown in this example.

Carpet swatches are prepared as in Example 4. The swatches are soaked for 3 minutes in 1% alumina so] at the temperatures shown in Table V, centrifuged to a wet pickup of and dried in air at room temperature. The alumina content of the dried fiber is 1%.

The swatches, along with a grafted, 66 nylon control which received no alumina treatment, are then subjected to the tumble test for 30 hours, three times as long as the normal test. The swatches are rated for pilling and fuzzing, with the results shown in Table V.

TABLE V Alumina used Soaking temp. Pill and fuzz rating EXAMPLE 6 A fabric woven from polyhexamethylene adipamide, modified with the sodium salt of acrylic acid, following the procedure of Example 3 to a carboxyl content of about 1100 equivalents 10 grams is immersed in water containing /2 by weight boehmite alumina. Fabric Sample A is immersed at 25 C. for three hours whereas Sample B is immersed for one hour at 100 C. Each sample is TABLE VI Before scour* After scour* 2%:::::::::::::::::::: i833 it? *Log R.

Aluminas which are eflective Aluminas which are effective in improving the pilling of the carpets described in the specification are, as stated hereinabove, those aluminas which are colloidal, have at least partially hydroxylated surfaces, and form a dispersion in a solvent, preferably water. Thus, they should have at least one dimension in the colloidal range when so dispersed. These aluminas show the best durability to washing, and maximum effectiveness in pilling reduction. In general, these aluminas are characterized by specific surface areas (excluding internal pores) greater than sq. meters/ gram, and preferably. greater than 100 sq. meters/ gram. In addition to the aluminas disclosed hereinabove, other aluminas are useful. As examples of these, there are the alpha aluminas, having surface areas from 20 to 70 sq. meters/ gram, such as those sold by the Aluminum Company of America, as aluminas A1 and A3; these have a nominal composition of 99% A1 0 and an alpha alumina content of about 80%. The ultimate particle diameters are about 0.25 micron, and the ultimate particle thickness is about 0.05 micron. Laminar alumina (sold by the Monsanto Chemical Company) is also useful for the process of this invention. This alumina is composed of plate-like particles consisting of a mixture of alpha and chi alumina.

Gamma aluminas produced especially by the burning of aluminum salts such as aluminum chloride are also useful. These aluminas are generally composed of almost spherical particles and have at least partially hydroxylated surfaces; they usually contain a small amount of residual anion such as chloride. The Alon-C used in the examples is typical of these aluminas. In addition, colloidal alpha alumina monohydrate (diaspore) may also be employed. Gamma alumina monohydrate ('boehmite) in which the particles are water-dispersi-ble platelets is useful in the process of this invention, in addition to the fibrous boehmite alumina already disclosed. Sols containing a mixture if gibbsite and boehmite alumina may also be employed. Fine particle size precipitated crystalline alumina hydroxides are also useful, and are exemplified by the alumina C-730. In addition to the above, alpha aluminum hydroxide (bayerite) may also be employed. This compound may be prepared by the action of water on aluminum at temperatures below 40 C., or by rapid precipitation from sodium aluminate by carbon dioxide at room temperature. Amorphous alumina gels are often suitable for treatment described herein, especially those which can be peptized with or without some heating to give alumina dispersions. Some of these dispersion contain extremely finely-divided gibbsite, bayerite or boehmite; the particles are usually too small to be visible even in the electron microscope. Other suitable alumina gels can be made from a variety of starting materials, the im- 12 portant features being that they be colloidal, readily dispersible and adhere strongly to the fibers. For any particular type of alumina, its ability to resist removal from the fiber by scouring, abrasion, etc., will be increased as the particle size is reduced. Preferably, all the particles should be dispersible in water to the colloidal state.

Preparation of the alumina sols The colloidal alumina suitable for treating the acidmodified polymer may be most suitably incorporated in aqueous sols and used for treatment in this medium; however, in addition to water, the products may be transferred and used as dispersed in organic solvents such as for example methyl ethyl ketone, acetone, acetonitrile, butyl acetate, dimethylformamide, Z-ethoxyethanol, propanol, ethylene glycol, glycerine, hydrocarbon oil fractions including for example kerosene, gasoline, naphtha and the like. Other organic solvents such as benzene, carbon tetrachloride, etc., are likewise suitable in some applications.

Method of sol application The alumina sols may be applied to the acid modified polymer surfaces in a variety of ways. For instance, a sol may contain from 0.1 to 10% of alumina but usually from about 0.1 to 3% by weight is more desirable. Broadly, the acid-modified polymer surfaces are contacted with the alumina sol and thereafter the coated surfaces are dried. This solution may be applied by dipping the fibrous article in a bath, sponging, spraying or by means of a roller.

After the surfaces have been treated with a liquid containing the alumina, the liquid evaporates in a preliminary drying step, leaving a deposit of fibrils or aggregates on the surface. Elevated temperatures, of course, accelerate this evaporation but this preliminary drying step may be carried out over a long period of time, if necessary at room temperature.

In order to increase adherence between the alumina and the acid-modified nitrogenous condensation polymer filaments, it is desirable to expose the alumina containing structures to a temperature of at least about C. and preferably about C. for a period of at least about 2 minutes before, during or after the drying step. This treatment may be suitably combined with the step in which the colloidal alumina is applied to the filaments, for example, by applying the sol at the boil. This method is espeially suitable when the sol is applied to skeins of yarn, tow, or staple and the like. Alternatively, when when treating fabricated articles such as carpets, it is often more satisfactory and convenient to expose them to steam or to dry heat after the sol treatment. As a guide in this respect, a two-minute exposure in steam or a one-hour exposure to dry heat at C. is satisfactory. Excessive exposure in temperature or time should be avoided, in order to avoid possible degradation of the fiber substrate.

It is usually desirable to scour the filament surfaces before applying the alumina sol in order to remove yarn finishes, sizes or the like which may interfere with adherence.

Treatment with the alumina sol may be applied to the filaments of nitrogenous condensation polymer at any stage of manufacture, before, during or after the acidgrafting step. Thus the sol may be applied to the continuous filaments, e.g., the tow, which is then cut and spun to yarn in conventional manner. Alternatively, the sol may be applied to the staple after the cutting operation, or at any stage of staple processing including application to the spun yarn. It is usually more desirable to apply the sol to the finished fabric or rug rather than to the staple or continuous filament tow, since the sol has a tendency to cause the fibers to adhere to one another. This tendency is desirable in the final rug, as

it contributes to resistance to pilling and fuzzing, but is less desirable when the fibers must be processed through carding, drafting, staple spinning and the like. In addition, where the yarn is subjected to conventional scouring or dyeing operations, some of the applied sol may be removed. Thus, better economy results from applying the sol to a finished fabric.

The alumina sol may be applied to the completed fabric, which may be of either woven or tufted construction. The sol gives advantageous results when applied to either a cut or loop pile carpet or rug, and application may be made before or after conventional latexing operations. Indeed, the application of the sol is so easily accomplished that it may be readily carried out in the home for rejuvenation purposes or after the new carpet has been installed, although usually it will be preferable for the manufacturer to carry out this step.

Although the preparation of the novel product of this invention has been described in terms of applying the alumina sol to filaments which are incorporated in a piletype fabric, improved resistance to pilling and fuzzing may also be obtained when such application is made to conventional woven or knitted staple fabric prepared from filaments of acid-grafted nitrogenous condensation polymer.

Polymer substrates Although any synthetic linear, high molecular weight, fiber-forming, nitrogenous organic condensation polymer is suitable for preparing the product of this invention, polyamides are preferred. Suitable polyamides are those synthetic linear polyamides which are prepared from polymerizable monoaminomonocarboxylic acids or their amide-forming derivatives, or from suitable diamine and suitable dicarboxylic acids or from amide-forming derivatives of these compounds. Polyamides wherein the intracarbonamide linkages are other than exclusively aromatic, i.e., there is at least 1 aliphatic -HCR- group in each repeating unit of the polymer molecule, are somewhat more readily acid-modified than the wholly aromatic type. The R group may be hydrogen, halogen, monovalent organic radical, alkylene or the like. Typical of such polyamides are those formed from an aliphatic diamine and an aliphatic acid and containing the repeating unit wherein -X and Y represent divalent aliphatic or cycloaliphatic groups and Z represents the linkage. Poly hexamethylene adipa-mide and polycaproamide (i.e., 66 and 6 nylons) are typical. Other suitable polyamides are those having the repeating structure wherein -A is a divalent aromatic radical and i and Z are as previously defined. Polyhexamethylene terephthalamide is illustrative of such polymers. Additionally polyamides having repeating units such as wherein B is divalent alkaryl (such as xylylene) may be used. Another class of suitable polyamides containing other than aromatic intracarbonamide repeating units are those prepared from piperazine, such as those from piperazine and adipic acid, piperazine and terephthalic acid and the like. In addition, wholly aromatic polyamides such as poly(m-phenylene isophthalamide) are suitable. Copolyamides, condensation copolymers wherein the amide linkage is the predominant linkage, and polyamide mixtures are also useful. As pointed out previously, such polyamides, to form the structures of the present invention, are of a high molecular Weight (i.e., they are fiber-forming and have a non-tacky surface at room temperature). Preparation of the high molecular weight polyamides is illustrated in United States Patent Nos. 2,071,250; 2,071,253 and 2,130,948. Preparation of polyurethanes is described in United States Patent Nos. 2,284,637 and 2,731,446; preparation of the polyureas is described in British Patent No. 535,139. Additional methods of preparation are described in United States Patent No. 2,708,617.

Acid modification of the polymer Any unsaturated organic acid is suitable for preparing the acid-modified polymer filament to which the alumina sol is applied. It is merely necessary that such acid contain one group with reactive aliphatic unsaturation. The most effective acids for carrying out the said modification are those of low molecular weight, since these more readily penetrate the polymer structure which is desirable for producing a modification extending throughout the filament. Suitable unsaturated monoacids are acrylic, methacrylic, ethylacrylic, cr-otonic, propiolic, and styrene canboxylic acids, for example. Diacids such as maleic, dichloromaleic, fumaric, butadiene dicarboxylic and itaconic are suitable. Derivatives readily convertible to acids may be employed, such as, for example, acid anhydrides, acid chlorides, esters, amides and the like. In addition to the carboxylic acids disclosed hereinabove, other acids are useful such as the sulfonic acids; (e.g., styrene sulfonic acid, ethylene sulfonic acid), unsaturated alkyl or aralkyl acid phosphates, phosphites, phosphonates and phosphinates; acid alkyl sulfates and carbonates with unsaturated carbon-carbon bonds also have utility. These acids may often be grafted as their preformed metal salts, thus avoiding necessity for this salt-forming step.

It is to be noted that the alumina sol can be elre-ctively applied to the acid-grafted polymer filament while it is in the acid form, or alternatively after it has been converted to the metallic salt, such as for example the sodium, calcium, magnesium or aluminum salt. The alumina treatment not only improves pilling and fuzzing, but it also appears to decrease the tendency for ion exchange; thus, there is less tendency for the sodium ion to be replaced by calcium ion when the acid-grafted fabric is exposed to tap water. This decreased tendency to ion exchange is beneficial where maximum antistatic effect is desired.

Many modifications of the above described invention will be apparent to those skilled in the art from a reading of the above without a departure from the inventive concept.

What is claimed is:

1. An article of manufacture comprising (a) a -coat ing of colloidal particles of hydrous alumina, deposited upon (b) filaments of an acid-grafted, water insoluble synthetic linear nitrogenous condensation polymer wherein recurring nitrogen atoms are an integral part of the polymer chain, at least the surface layer of the said filaments being modified to contain, for each million grams of polymer, at least 300 equivalents of organic radicals selected from the group consisting of non-phenolic acid and metallic salt of the said acid, chemically bonded by carbon-carbon bonds to the said polymer, the said coating consisting of from about 0.5 to about 5% by weight of the said article.

2. The article of claim 1 wherein the nitrogenous condensation polymer is a polyamide.

3. The article of claim 2 wherein the polyamide is polyhexamethylene adipamide.

15 16 4. The article of claim 1 wherein the colloidal par- References Cited by the Examiner ticles of hydrous alumina are at least two dimensions UNITED STATES PATENTS less than about 0.2 micron.

5. The article of claim 4 wherein the hydrous alumina 290L218 2/1955 Nkfkerson 1171388 5 6. 1 1i d 1" ugos i- The artlc 6 of C a In 4 Wh r ln the hy rous a umma 31 7/1963 Tanner 260 2IS particles are fibrous.

7. The article of claim 1 in the form of a fabric.

8. The fabric of claim 7 in the form of a rug. WILLIAM MARTIN Primary Examiner 

1. AN ARTICLE OF MANUFACTURE COMPRISING (A) A COATING OF COLLOIDAL PARTICLES OF HYDROUS ALUMINA, DEPOSITED UPON (B) FILAMENTS OF AN ACID-GRAFTED, WATER INSOLUBLE SYNTHETIC LINEAR NITROGENOUS CONDENSATION POLYMER WHEREIN RECURRING NITROGEN ATOMS ARE AN INTEGRAL PART OF THE POLYMER CHAIN, AT LEAST THE SURFACE LAYER OF THE SAID FILAMENTS BEING MODIFIED TO CONTAIN, FOR EACH MILLION GRAMS OF POLYMER, AT LEAST 300 EQUIVALENTS OF ORGANIC RADICALS SELECTED FROM THE GROUP CONSISTING OF NON-PHENOLIC ACID AND METALLIC SALT OF THE SAID ACID, CHEMICALLY BONDED BY CARBON-CARBON BONDS TO THE SAID POLYMER, THE SAID COATING CONSISTING OF FROM ABOUT 0.5 TO ABOUT 5% BY WEIGHT OF THE SAID ARTICLE. 